1. Field of the Invention
The present invention relates to a piston of a gasoline direct injection engine, and more particularly to a piston of a gasoline direct engine that stratifies an air-fuel mixture through efficient tumble flow thereof.
2. Description of Related Art
Generally, a gasoline direct injection engine directly injects gasoline fuel into a combustion chamber thereof to combust therein.
In designing a gasoline direct injection engine, an important factor is the intake flow of air-fuel mixture, and the intake flow is determined by an intake port, a combustion chamber, and a piston shape.
Further, the intake flow is made to prevent the injected fuel from colliding with the piston surface, to appropriately mix the air-fuel to be evaporated, to optimize the atomization thereof, and to stratify the air-fuel mixture, and related investigations have been actively undertaken.
Particularly, the combustion chamber includes the upper surface of the piston together with the lower surface of a cylinder head, and the air that flows in through the intake port and the fuel that is injected into the combustion chamber during the compression stroke are mixed to form an air-fuel mixture such that the flow thereof is stratified to be combusted.
Further, the piston of the gasoline direct injection engine is developed to securely stratify the air-fuel mixture according to the engine load and the speed thereof.
A bowl of the upper surface of the piston has a uniform curvature according to the conventional art to form a gentle sphere surface such that the tumble flow is weak, and therefore there is a problem in stratifying the air-fuel mixture around a spark plug by second fuel injection and first fuel injection for optimizing flow.
Also, when the fuel that is injected through the injector collides with the bottom surface of the bowl of the piston, it takes a long time for the attached fuel to evaporate such that soot and hydrocarbons are increased.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.